Washington (CNN) -- Thousands of firearms have gone missing from manufacturers' inventories since 2009 "without a record of being legally sold," according to a report released Thursday by a gun control advocacy group.

The report by the Brady Center to Prevent Gun Violence put the number of missing weapons at 16,485.

"It is shocking that gun makers are so oblivious to public safety that they lose track of thousands of guns every year," Henigan, acting president of the Brady Center, said in a statement. "Given the lethality of its product, the gun industry has a special duty to act responsibly. Instead, it has a scandalous record of carelessness."

The Brady Center report suggests that some guns may never have had serial numbers stamped into them, making them virtually impossible to trace. The group says that the missing guns are often used by criminals precisely because they are so hard to trace.

The report does not mention which manufacturers are reported to having missing firearms. The Brady Center says the data was collected from a Bureau of Alcohol, Tobacco, Firearms and Explosives report that was presented to the gun industry last month.

But the report also states that ATF conducts their compliance examinations at only about 20% of gun dealers and manufacturers each year, and says as a result, "The 16,485 'missing' guns are likely a vast undercount of the total number of guns that disappeared from gun manufacturers in the last two and a half years."

Andrew Molchan, Publisher of American Firearms Industry Magazine, slammed the report in a statement to CNN.

"The Brady spin and implication that some manufacturers, whose names are not mentioned so we can't check the charges, are knowingly selling guns before they are logged into the manufacturer's records is absolutely ridiculous," Molchan said.

According to ATF statistics, more than 5 million firearms were made in the United States in 2008 by about 4,487 manufacturers. The federal law enforcement agency is in charge of inspecting companies that make and sell firearms to make sure they are in compliance with federal laws.

The ATF says about 600 agents did more than 10,000 inspections last year, but the Brady Center says the agency isn't able to do enough because it lacks manpower and money.

The ATF said it had not read the report and would not comment.

The Brady Center is an advocacy group for tightened gun laws and was named after Jim Brady, President Ronald Reagan's press secretary, who was shot in the head in the attempted assassination of Reagan in 1981.